Molecular consequences of altered neuronal cholesterol biosynthesis.
The first dedicated step in de novo cholesterol biosynthesis begins with formation of squalene and ends with the reduction of 7-dehydrocholesterol by 7-dehydrocholesterol reductase (Dhcr7) into cholesterol, which is an essential structural and signaling molecule. Mutations in the Dhcr7 gene lead to Smith-Lemli-Opitz syndrome (SLOS), which is characterized by developmental deformities, incomplete myelination, and mental retardation. To understand better the molecular consequences of Dhcr7 deficiency in neuronal tissue, we analyzed the effect of cholesterol deficiency on the transcriptome in Neuro2a cells. Transient down-regulation of Dhcr7 by siRNA led to altered expression of multiple molecules that play critical roles in intracellular signaling or vesicular transport or are inserted into membrane rafts (e.g. Egr1, Snx, and Adam19). A similar down-regulation was also observed in stable Dhrc7-shRNA-transfected cell lines, and the findings were verified by qPCR. Furthermore, we investigated the Dhcr7-deficient and control cells for the expression of several critical genes involved in lipid biosynthesis. Among these, fatty acid synthase, sterol-regulatory element binding protein 2, SREBF chaperone, site-1 protease, and squalene synthase showed a significant down-regulation, suggesting that, in a neuronal cell line, Dhcr7 is a potent regulator of lipid biosynthesis. Importantly, the gene expression changes were present in both lipid-containing and cholesterol-deficient media, suggesting that intrinsic cholesterol biosynthesis is necessary for normal neuronal function and cannot be supplemented from extrinsic sources.
Korade
Zeljka
Z
Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, USA. zeljka.korade@vanderbilt.edu
Kenworthy
Anne K
AK
Mirnics
Károly
K
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D002784:Cholesterol / Q000096:biosynthesis* / Q000378:metabolism; D015536:Down-Regulation; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D043484:Proprotein Convertases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D051782:Sterol Regulatory Element Binding Protein 2 / Q000378:metabolism; D013261:Sterols / Q000378:metabolism; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000378:metabolism
D005227:Fatty Acids; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D051782:Sterol Regulatory Element Binding Protein 2; D013261:Sterols; D033921:Vesicular Transport Proteins; D002784:Cholesterol; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase; D064429:Fatty Acid Synthases; D013186:Farnesyl-Diphosphate Farnesyltransferase; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; C115575:membrane-bound transcription factor peptidase, site 1